1. Field
The present disclosure relates to a fuel cell stack.
2. Description of the Related Art
For example, a solid polymer electrolyte fuel cell includes a solid polymer electrolyte membrane that is made from a solid polymer ion-exchange membrane. A power generation cell of this type includes a membrane electrode assembly (MEA) and a pair of separators (bipolar plates) sandwiching the MEA therebetween. The MEA includes a solid polymer electrolyte membrane and an anode electrode and a cathode electrode sandwiching the solid polymer electrolyte membrane therebetween. Each of the anode electrode and the cathode electrode includes an electrode catalyst (electrode catalyst layer) and porous carbon (gas diffusion layer). A predetermined number of such power generation cells are stacked so as to form a fuel cell stack, which is used, for example, as an automobile fuel cell stack.
In order to obtain a desired power, fuel cells are usually used in the form of a fuel cell stack in which a predetermined number (for example, several tens to several hundreds) of power generation cells are stacked. In the fuel cell stack, it is necessary to press the stacked power generation cells against each other in order to suppress an increase in the internal resistance of the power generation cells and a reduction in the sealability against a reactant gas.
Each of the power generation cells includes a power generation portion located in its central part and a manifold portion, for sealing manifolds, located in its peripheral part. The optimal clamp load to be applied to the power generation portion differs from the optimal clamp load to be applied to the manifold portion.
Japanese Patent No. 4494830, for example, describes a fuel cell stack that can reliably apply a desired load to each of a power generation portion and a manifold portion of each of power generation cells with a simple and economical structure.
The fuel cell stack includes an insulating spacer and a terminal member that are disposed at least at one end of the power generation cells in a stacking direction. The insulating spacer is disposed in direct contact with an end plate of a box-shaped casing, and applies a load to the manifold portion. The terminal member is disposed inside of the insulating spacer, and applies a load to the power generation portion. The terminal member is disposed in a recessed portion that is formed in a central part of the insulating spacer. A load applied to the power generation portion or to the manifold portion is adjusted by adjusting the thickness of the terminal member.